A conventional built-in antenna will be described as follows with reference to Japanese Patent Laid-Open Application No. H01-228303. FIG. 8 shows an inverted-F antenna which has been conventionally used as a built-in antenna. The inverted-F antenna is formed of ground plate 104, radiating element 101, shortcircuit part 102 to shortcircuit between ground plate 104 and radiating element 101, and power feed part 103 to feed electric power into the antenna. To broaden the bandwidth of the conventional inverted-F antenna has required either extending the distance between radiating element 101 and ground plate 104 or increasing radiating element 101 in size. However, in the aforementioned inverted-F antenna, when the device having the antenna inside is designed to be thinner, it becomes impossible to secure the distance between ground plate 104 and radiating element 101 because ground plate 104 and a printed circuit board are laid horizontally, thereby making it difficult to broaden the bandwidth.